Many communication systems utilize high performance cables normally having four pairs or more that typically consist of two twisted pairs transmitting data and two receiving data as well as the possibility of four or more pairs multiplexing in both directions. A twisted pair is a pair of conductors twisted about each other. A transmitting twisted pair and a receiving twisted pair often form a subgroup in a cable having four twisted pairs. High-speed data communications media in current usage includes pairs of wire twisted together to form a balanced transmission line as well as the possibility of four or more pairs multiplexing in both directions. Optical fiber cables may include such twisted pairs or replace them altogether with optical transmission media (fiber optics).
In conventional cable, each twisted pair of conductors for a cable has a specified distance between twists along the longitudinal direction. That distance is referred to as the pair lay. When adjacent twisted pairs have the same pair lay and/or twist direction, they tend to lie within a cable and when twisted pairs are closely placed, such as in a communications cable, electrical energy may be transferred from one pair of a cable to another adjacent or outlying pair and this energy transfer between conductor pairs is undesirable and referred to as crosstalk. Therefore, in many conventional cables, each twisted pair within the cable has a unique pair lay in order to increase the spacing between pairs and thereby also reducing the cross-talk between twisted pairs of a cable. Additionally undesirable energy may be transferred between adjacent cabling conductors which is known as alien cross-talk or alien near-end cross talk (anext).
The Telecommunications Industry Association and Electronics Industry Association have defined standards for crosstalk, including TIA/EIA-568 A, B, and C including the most recent edition of the specification. The International Electrotechnical Commission has also defined standards for data communication cable crosstalk, including ISO/IEC 11801. One high-performance standard for 100 MHz cable is ISO/IEC 11801, Category 5. Additionally, more stringent standards are being implemented for higher frequency cables including Category 6 and Category 7, which includes frequencies of 200 and 600 MHz, respectively and the most recent proposed industrial standard raising the speeds to 10 Gbit (10 GBASE-T) over copper with Ethernet or other cable designs. Industry standards cable specifications and known commercially available products are listed in Table 1 and a set of updated standards is forthcoming from the EIA committee and should be considered as part of this disclosure. IEEE 802.3(a)(f) was presented as a topic of discussion in the Nov. 14-19, 2004 IEEE plenary session and includes topics such as Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications, Data Terminal Equipment (DTE) and Power via Media Dependent Interface (MDI). Changes to MDI most pertinent to the present invention is that even low power conductors may emit undesirable energy into the twisted pair conductors promoting undesirable cross-talk between the power source and the communications conductors. As higher power is allowed in the MDI and data bit rates increase, the communications conductors become even more susceptible to cross-talk and data transmission reliability issues. Present Category 6 standards are listed in Tables 2A-2G.
Another feature of this invention will be to selectively add conductive materials in appropriate amounts to non-conductive or semi-conductive materials that comprise the separator structure (prior to roll-up or after roll-up depending on the design of choice) in order to attenuate any cross talk between the conductor and other communications or power conducting cables. Additionally, when conductive material is added to the configuration of the separators of the present invention, this would act as a shield against alien near end cross talk (anext), or stray interference from adjacent cables or from disrupting communication signals from adjacent cables (far end crosstalk—fext).
Addition of conductive materials (metallization and the like) in relatively small concentrations either within the insulation of the separators or on exterior surfaces also decreases the weight of the cable. Presently, shielding, such as aluminized Mylar®, on curved linear surfaces is difficult in that it provides for unique and costly designs. This invention minimizes this difficulty by allowing for application of the aluminized film (PE, PET, Mylar®, etc.) on a flat or ribbon configuration prior to adding curved linearity to provide (upon roll-up) the cable support-separator.
Cabling exists today that is claimed to operate reliably without cross talk between the power cable and the communication cables at 48VDC and up to 12 W (0.25 A). As the IEEE looks forward to providing the next generation of cable standards, the need for higher power is becoming a reality. Cabling that will enable up to 60VDC and 30 W, within a cable structure comprising fiber optic or twisted pair communications, and no crosstalk between the power cable and the communications lines as well as ensuring reliable communications operation (not subject to alien cross talk from other communications cable), is required. This invention discloses several cabling and separator system configurations allowing for component constructions that will meet the newly proposed IEEE standards.
TABLE 1INDUSTRY STANDARD CABLE SPECIFICATIONSTIA CAT 6ANIXTER XP6ANIXTER XP7DRAFT 10R3.00XPR3.00XPALL DATA AT 100 MHzTIA CAT 5eNov. 15, 2001November 2000November 2000MAX TEST FREQUENCY100MHz250MHz250MHz350MHzATTENTUATION22.0db19.8db21.7db19.7dbPOWER SUM NEXT32.3db42.3db34.3db44.3dbACR13.3db24.5dbPOWER SUM ACR10.3db22.5db12.6db23.6dbPOWER SUM ELFEXT20.8db24.8db23.8db25.8dbRETURN LOSS20.1db20.1db21.5db22.5db
TABLE 2AReturn Loss Requirements for Category 6 CableReturn loss @ 20° C. ± 3° C. (68° F. ± 5.5° F.),worst pair for a length of 100 m (328 ft)Frequency MHzCategory 6 dB1 ≦ ƒ ≦ 1020 + 5 log (ƒ)10 ≦ ƒ ≦ 202520 ≦ ƒ ≦ 25025 − 7 log (ƒ/20)
TABLE 2BInsertion Loss Requirements for Category 6 CableInsertion loss @ 20° C. ± 3° C. (68° F. ± 5.5° F.),worst pair for a length of 100 m (328 ft)Frequency MHzCategory 6 dB.7721.810.06.0250.032.8
TABLE 2CNear End Crosstalk Requirements For Category 6 CableHorizontal cable NEXT loss @ 20° C. ± 3° C. (68° F. ± 5.5° F.),worst pair-to-pair, for a length of 100 m (328 ft)Frequency MHzCategory 6 dB0.15086.710.059.3250.038.3
TABLE 2DPower Sum Near End Crosstalk Requirementsfor Category 6 CablePSNEXT loss @ 20° C. ± 3° C. (68° F. ± 5.5° F.),for a length of 100 m (328 ft)Frequency MHzCategory 6 dB0.15084.710.057.3250.036.3
TABLE 2EEqual Level Near End Crosstalk RequirementsFor Category 6 CableELNEXT loss @ 20° C. ± 3° C. (68° F. ± 5.5° F.),worst pair-to-pair for a length of 100 m (328 ft)Frequency MHzCategory 6 dB.77270.010.047.8250.019.8
TABLE 2FPower Sum Equal Level Near End CrosstalkRequirements for Category 6 CablePSELNEXT loss @ 20° C. ± 3° C. (68° F. ± 5.5° F.),for a length of 100 m (328 ft)Frequency MHzCategory 6 dB.77267.010.044.8250.016.8
TABLE 2GProposed Requirements for Alien Near -endCross-talk for Category 6 CableProposed Requirement for Channel PowerSum Alien Near-End Cross-talkFrequencyCategory 6 dBPSANEXT ≧ 60 − 10log(ƒ)1 ≦ ƒ ≦ 100 MHzPSANEXT ≧ 60 − 15log(ƒ)100 ≦ ƒ ≦ 625 MHz
In conventional cable, each twisted pair of conductors for a cable has a specified distance between twists along the longitudinal direction. That distance is referred to as the pair lay. When adjacent twisted pairs have the same pair lay and/or twist direction, they tend to lie within a cable more closely spaced than when they have different pair lays and/or twist direction. Such close spacing increases the amount of undesirable cross-talk that occurs. Therefore, in many conventional cables, each twisted pair within the cable has a unique pair lay in order to increase the spacing between pairs and thereby to reduce the cross-talk between twisted pairs of a cable. Twist direction may also be varied.
Along with varying pair lays and twist directions, individual solid metal or woven metal air shields are used to electro-magnetically isolate pairs from each other or isolate the pairs from the cable jacket or low power conduction. Shielded cable exhibits better cross-talk isolation but is more time consuming and costly to manufacture, install, and terminate. Individually shielded pairs must generally be terminated using special tools, devices and techniques adapted for the job, also increasing cost and difficulty.
One popular cable type meeting the above specifications is Unshielded Twisted Pair (UTP) cable. Because it does not include shielded pairs, UTP is preferred by installers and others associated with wiring building premises, as it is easily installed and terminated. However, UTP fails to achieve superior cross-talk isolation such as required by the evolving higher frequency standards for data and other state of the art transmission cable systems, even when varying pair lays are used.
Another popular cable type is the “Banana Peel®” cable manufactured by Belden Electronics and published as PCT Application WO2004/021367A3 which allows the user to “peel” individual conductor sets from the central core cable support-separator. The wire jackets are bonded together with a suitable adhesive. This design aids in stripping and termination of the individual conductive media by the installer.
Some cables have used supports in connection with twisted pairs. These cables, however, suggest using a standard “X”, or “+” shaped support, hereinafter both referred to as the “X” support. Protrusions may extend from the standard “X” support. The protrusions of these prior inventions have exhibited substantially parallel sides.
The document, U.S. Pat. No. 3,819,443, hereby incorporated by reference, describes a shielding member comprising laminated strips of metal and plastics material that are cut, bent, and assembled together to define radial branches on said member. It also describes a cable including a set of conductors arranged in pairs, said shielding member and an insulative outer sheath around the set of conductors. In this cable the shielding member with the radial branches compartmentalizes the interior of the cable. The various pairs of the cable are therefore separated from each other, but each is only partially shielded, which is not so effective as shielding around each pair and is not always satisfactory.
The solution to the problem of twisted pairs lying too closely together within a cable is embodied in three U.S patents U.S. Pat. No. 6,150,612 to Prestolite, U.S. Pat. No. 5,952,615 to Filotex, and U.S. Pat. No. 5,969,295 to CommScope incorporated by reference herein, as well as an earlier similar design of a cable manufactured by Belden Wire & Cable Company as product number 1711A. The prongs or splines in the Belden cable provide superior crush resistance to the protrusions of the standard “X” support. The superior crush resistance better preserves the geometry of the pairs relative to each other and of the pairs relative to the other parts of the cables such as the shield. In addition, the prongs or splines in this invention preferably have a pointed or slightly rounded apex top which easily accommodates an overall shield. These cables include four or more twisted pair media radially disposed about a “+” -shaped core. Each twisted pair nests between two fins of the “+” -shaped core, being separated from adjacent twisted pairs by the core. This helps reduce and stabilize crosstalk between the twisted pair media. U.S. Pat. No. 5,789,711 to Belden describes a “star” separator that accomplishes much of what has been described above and is also herein incorporated by reference.
However, these core types can add substantial cost to the cable, as well as excess material mass which forms a potential fire hazard, as explained below, while achieving a crosstalk reduction of typically 3 dB or more. This crosstalk value is based on a cable comprised of a fluorinated ethylene-propylene (FEP) insulated conductors with PVC jackets as well as cables constructed of FEP jackets with FEP insulated conductors. Cables, where no separations between pairs exist, will exhibit smaller cross-talk values. When pairs are allowed to shift based on “free space” within the confines of the cable jacket, the fact that the pairs may “float” within a free space can reduce overall attenuation values due to the ability to use a larger conductors to maintain 100 ohm impedance. The trade-off with allowing the pairs to float is that the pair of conductors tend to separate slightly and randomly. This undesirable separation contributes to increased structural return loss (SRL) and more variation in impedance. One method to overcome this undesirable trait is to twist the conductor pairs with a very tight lay. This method has been proven impractical because such tight lays are expensive and greatly limit the cable manufacturer's throughput and overall production yield. An improvement included by the present invention to structural return loss and improved attenuation is to provide grooves within channels for conductor pairs such that the pairs are fixedly adhered to the walls of these grooves or at least forced within a confined space to prevent floating simply by geometric configuration. This configuration is both described here within and referenced in U.S. Pat. No. 6,639,152 filed Aug. 25, 2001 as well as the international application PCT/US02/13831 filed at the United States Patent and Trademark Office on May 1, 2002. Both the patent and the pending application are hereby specifically incorporated by reference.
In addition to the preceding portion of the invention, U.S. Pat. Nos. 6,680,922, 5,887,243, 5,444,184, 5,418,878, and 6,751,441 are hereby also incorporated by reference regarding the use of lower voltage power conductors for wireless fidelity applications and the like.
U.S. Pat. No. 6,680,922 refers to a packet-centric wireless point to multi-point telecommunications system comprising a wireless base station coupled to a data network, workstations, subscriber customer premise equipment (CPE) in wireless communication, sharing a wireless bandwidth using a packet-centric protocol and at least one layer above layer 4 of Open Systems Interconnect (OSI) model.
U.S. Pat. No. 5,887,243 includes a method of generating and delivering an individualized mass medium program presentation at a receiver station, a computer for generating and communicating information, and at least one output device operatively connected to a viewer with at least one data storage location.
U.S. Pat. No. 5,444,184 references an apparatus for transmitting communication signals and electrical power signals between two remote locations, comprising at least two twisted pairs having at least one twisted pair for transmitting the communication signals, and having conductors connected in parallel for transmitting electrical power signals; and a transformer means being connected to at least two twisted pairs for separating the transmission of the communication signals and the electrical power signals. The patent describes a communication cable that has at least two twisted pairs and at least two power conductors and may further comprises three paired power conductors for transmission of three phase power, the three paired power conductors being used for transmitting three communication channels.
U.S. Pat. No. 5,418,878 describes an invention that seeks to provide an electrical telecommunications cable construction in which pair-to-pair capacitance unbalance and cross-talk is minimized. Accordingly, this invention provides an electrical telecommunications cable comprising a plurality of pairs of individually insulated conductors, the conductors in each pair twisted together, and spacer means holding the pairs of conductors spaced apart. The spacing means is provided by projections extending inwardly from the jacket or outwardly and are spaced circumferentially around the jacket to provide spacers so the pairs of conductors are separated from one another by the projections.
U.S. Pat. No. 6,751,441 describes a premises, connected to receive broadband service(s) and also connected to a cable system, and provides a broadband interface which connects to in-premises cabling which is coupled to consumer receivers such as television sets, PDAs, and laptops. Connected to the broadband interface is an adjunct device which channels broadband, data and voice signals supplied to an in-premises wireless system as distinguished from the signals supplied to the cable connected consumer receivers. The adjunct device formats the broadband and voice signals or any broadband service into packet format suitable for signal radiation and couples them to the in-premises coax cabling, via a diplexer, at a selected location. At a second cable location a second diplexer, connected to the cable, separates the broadband, data and voice signals and couples them to a signal radiation device (i.e., an RF antenna or leaky coaxial cable) that radiates the signal to the immediate surrounding location. Various devices, near the second cable location for specific services, receive the wireless signals (i.e., broadband, data and voice) from the radiating antenna.
U.S. Pat. No. 6,596,544 by Clark, et. al., and assigned to CDT/Mohawk, describes a data cable comprising a non-conductive central core providing channels for a plurality of twisted pairs of conductors all enclosed in a non-conductive unshielded jacket.
U.S. Pat. No. 6,596,503 by Clark, et. al., and assigned to CDT/Mohawk, describes a method of inserting communication media onto the channels for constructing a data communications cable.
U.S. Pat. No. 4,605,818 by Arroyo, et. al., and assigned to AT&T/Bell Labs, describes a cable construction comprising a central core, data communications media and a jacket enclosing the core and communications media wherein the jacket is comprised of an impregnated woven material, with impregnative additives proportional to the number and type of media to resist heat, effectively delaying the decomposition of the media and core enclosed within.
U.S. Pat. No. 6,008,455 by Lindstrom, et. al., and assigned to Ericsson, describes fixating three or more conductors in a mutually parallel and spaced relationship to minimize data transmission skew and to avoid bit error.
U.S. Pat. No. 4,271,104 by Anderson, et. al., and assigned to Honeywell, describes a method for producing a unitary ribbon like sheet of optic fiber which is effectively optically separated into a plurality of parallel optical paths forming the optically transparent material into a ribbon like sheet.
U.S. Pat. No. 6,818,832 by Hopkinson, et. al., and assigned to Commscope Solutions Properties, LLC, describes a cable comprising a plurality of twisted pairs of conductors and a crossweb running longitudinally along at least a portion of a length of the twisted pairs of conductors wherein at least one of the fins has a substantially elliptical shape thereby spacing the adjoining conductor pair at a maximum spacing within a cable.
U.S. Pat. No. 6,365,836 by Blouin, et. al., and assigned to NORDX/CDT, describes a generally cross-shaped core with a plurality of twisted pairs of insulated conductors with each twisted pair of insulated conductors in stable positions apart from each other and a jacket generally surrounding the plurality of twisted pairs of insulated conductors and the core being held at a distance away from adjacent cabling as defined by the jacket outer surface.
U.S. Pat. No. 6,091,025 by Cotter, et. al., and assigned to Khamsin Technologies, LLC, describes core support-separators comprising two identical portions that when placed back to back define a quadrant cross-section of channels in which to place twisted pairs of communication media.
U.S. Pat. No. 4,755,629 by Beggs, et. al., and assigned to AT&T/Bell Labs, describes a communications cable, which comprises a dielectric material and which includes a plurality of portions each of which is associated individually with a pair of the conductors. Each of the dielectric portions have a thickness which is equal at least to the radius of the metallic conductor of an associated insulated conductor to suitably space each pair of insulated conductors.
U.S. Pat. No. 6,748,146 by Parris, and assigned to Corning Cabling Systems, describes at least one optical fiber being at least partially embedded within at least one material with at least one material forming a housing that protects the optical fiber.
U.S. Pat. No. 6,855,889 by Gaeris, and assigned to Belden Wire & Cable Co., describes a twisted-pair cable separator spline comprising: a longitudinally extending spline having a plurality of spaced longitudinally extending open pockets, a cross-section of said spline having a major axis and a minor axis and at least one pocket being on the major axis, and at least one pocket being on the minor axis, and wherein the major axis has a length greater than a length of said minor axis.
U.S. Pat. No. 6,812,418 by Clark, et. al., and assigned to CDT/Mohawk, describes a configurable tape separator that separates the first twisted pair of insulated conductors from the second twisted pair of insulated conductors without completely surrounding any one twisted pair of the plurality of twisted pairs of insulated conductors all enclosed within a surrounding sheath.
U.S. Pat. No. 6,800,811 by Boucino, and assigned to Commscope Solutions Properties, LLC, describes a communications cable comprising a cable jacket and a spacer extending within the cable jacket with the spacer having a longitudinally extending center portion and plurality of longitudinally extending wall portions radiating from the center portion with the longitudinally extending wall portions increasing in thickness over only a portion of the walls wherewith, within a jacket, the spacer and the cable jacket defining a plurality of compartments for the twisted pair of conductors.
U.S. Pat. No. 6,686,537 by Gaeris, et. al., and assigned to Belden Wire & Cable Co., describes an individual bound lateral shielded twisted pair data cable and a first composite tape having a non-metal base and a layer of metal on one side of the base, and a second composite tape having a non-metal base and a layer of metal on both sides of the base and wrapped around a twisted pair of conductors.
U.S. Pat. No. 5,146,528 by Gleim, et. al., and assigned to Deutsch Thompson-Brandt Gmbh, describes a cable for conducting simultaneously electricity and light comprised of optically conductive material for conducting light therethrough, so that electrical signals can be conducted through said core simultaneously with light signals through said insulation layer.
U.S. Pat. No. 6,792,184 by Conrad, et. al., and assigned to Corning Cabling Systems, describes a fiber optic ribbon having plurality of optical fibers arranged in a generally planar configuration.
U.S. Pat. No. 6,689,958 by McKinney, et. al., and assigned to Parlex Corp., describes a ribbon cable having a length and a width where the ribbon cable comprises a plurality of parallel spaced conductors located in a first plane, each of the plurality of conductors having conductor end portions at opposing ends and a central conductor portion between the conductor end portions, the conductor end portions having a generally circular cross section and a drain wire located generally in a second plane spaced from the first plane by a predetermined distance and a conductive shield layer laminated to one of the opposing surfaces of an insulating material and the shield layer being conductively coupled to the drain wire.
US patent application 20050063650A1 by Castellani, et. al., describes a telecommunication cable comprising a tubular element of polymeric material and at least one transmission element housed within.
US patent application 20040217329A1 by Easter, et. al., describes a semiconductive resin layer in contact with a crosslinked wire and cable insulation layer, wherein the insulation layer is crosslinked using a peroxide cure system to lightly bond the semiconductive resin layer and cable insulation layer.
US patent application 20040149483A1 by Glew, and assigned to Cable Components Group, LLC., describes communications cable comprising an interior support, a central region with an external radial and axial surface, and an interior support comprising at least one anvil shaped core support-separator section radially and axially defined by the central region.
US patent application 20050006133A1 by Greiner, et. al., describes a multiconductor arrangement for either power or data transmission.
US patent application 20050006132A1 by Clark, and assigned to CDT/Mohawk, describes a method of manufacture of a data cable wherein the step of extruding the core includes stretching the core material at a plurality of intervals during extrusion so as to form a corresponding plurality of pinch points along a length of the core such that a diameter of the core at the pinch points is substantially reduced relative to a maximum diameter of the core.
US patent application 20050051355A1 by Bricker, et. al., describes a jacket comprising at least one spline projecting inward from an inner surface of the jacket, wherein at least a portion of a conductive twisted pair is positioned between the spline and a center core, thereby preventing relative movement of the jacket with respect to the core.
US patent application 20050029007A1 by Nordin, et. al., and assigned to Panduit Corp., describes a system for reducing alien crosstalk in a communication network via patch cords to attenuate signals between communications media.
US patent application 20050023028A1 by Clark, describes data communication cable comprising: a plurality of twisted pairs of insulated conductors, each twisted pair comprising two electrical conductors, each surrounded by an insulating layer and twisted together to form the twisted pair; and a jacket substantially enclosing the plurality of twisted pairs of insulating conductors; wherein the insulating layer includes a dielectric material comprising a plurality of micro-particles.
US patent application 20040216914A1 by Gavriel, et. al., and assigned to NORDX/CDT, describes a cable wire comprising a conductor and at least one inner insulating layer surrounding the conductor with at least one of the inner layers being a nano-composite comprising nano-sized platelets and a flame and smoke retardant additive package dispersed within a polyolefin matrix.
US patent application 20040118593A1 by Augustine, et. al., describes an electrical data cable having reduced crosstalk characteristics comprising at least two generally flat tape separators placed in between the plurality of twisted conductor pairs.
US patent application 20040055781A1 by Cornibert, et. al., and assigned to NORDX/CDT, describes a cable separator spline wherein a pair of longitudinally extending walls includes a first wall substantially thicker than a second wall.
US patent application 20040055779A1 by Wiekhorst, et. al., describes a cable construction of components extending along a longitudinal axis and including at least one first channel wherein the component is grooved.
US patent application 20040256139A1 by Clark, et. al., describes an insulated conductor comprising a conductive core and a first insulating layer surrounding the conductive core and the conductive core has an irregularly shaped outer circumference.
US patent application 20050056454A1 by Clark, describes a cabling scenario wherein a first twisted pair of conductors is wrapped with an insulative material of a measured dielectric constant, a second twisted pair of a second dielectric constant and a third pair of a third dielectric constant by wrapping the twisted pairs with cumulative layers of various dielectric constant electrical properties.
U.S. Pat. No. 5,821,466 by Clark, et. al., describes a cable system whereby a first twisted pair of conductors is wrapped in a second pair of twisted pair of conductors with substantial contact and a third twisted pair of conductors is substantially wrapped around the second twisted pair of conductors to increase mechanical stability of the concentrically twisted pairs of conductors.
U.S. Pat. No. 5,544,270 by Clark, et. al., describes a twisted pair of conductors substantially wrapped around a central core and a jacket wherein a second pair of twisted conductors is wrapped around the first and subsequently wrapped in a second jacket.
International patent application WO2004/021,367 by Schuman, et. al., and assigned to Belden Technologies, describes multi-member cables which are compromised of jacketed cables whose jackets are adhered together without the use of an adhesive element, such as by co-forming the jackets, and methods for manufacturing such cables are also discussed. Generally, the components will be separated from the mufti-member cable by an installer.
International patent application WO1996/024143 by Hardie, et. al., and assigned to W L Gore, describes a high speed data transmission with a cable differential pair comprising two conductors generally 180 degrees apart from each other wherein the distance between any of the conductors and the shield is substantially equal to or greater than the distance between that conductor and the center axis of the cable.
International patent application WO2004/042446A1 by Ishikawa, et. al., and assigned to and assigned to Sumitomo Electric Inc. Ltd., describes an optical fiber ribbon comprising a plurality of optical fibers which are arranged in parallel and a resin which integrates the plurality of optical fibers over the whole length of the optical fibers.
Japan patent application JP07122123A2 by Kazuhiro, et. al., and assigned to Sumitomo Electric Co, Ltd., describes a ribbon cable that is rolled to form a unit cable around a central core.
European patent application EP0957494B1 by Keller, and assigned to Alcatel, describes a composite cable for providing electrical signals and optical signals comprising twisted pairs of wires and optical fiber media.
Finally, U.S. Pat. No. 4,523,970 by Toy, and assigned to Raytheon, and hereby incorporated by reference into the body of this specification, describes the use of ethylene-vinyl acetate copolymer and ethylene-vinyl acetate-methacrylic acid terpolymer and a rubber component comprising butyl rubber to provide am adhesive-like inner surface of components that are extruded. The use of this “tacky” adhesive like surface is part of the instant invention in that the cable and/or support-separator can make use of this technique to ensure that conductive and non-conductive media may be intentionally placed properly and also removed as desired during installation.
A broad range of electrical conductors and electrical cables are installed in modern buildings for a wide variety of uses. Such uses include data transmission between computers, voice communications, as well as control signal transmission for building security, fire alarm, and temperature control systems. These cable networks extend throughout modern office and industrial buildings, and frequently extend through the space between the dropped ceiling and the floor above. Ventilation system components are also frequently extended through this space for directing heated and chilled air to the space below the ceiling and also to direct return air exchange. The space between the dropped ceiling and the floor above is commonly referred to as the plenum area. Electrical conductors and cables extending through plenum areas are governed by special provisions of the National Electric Code (“NEC”).
In building designs, many precautions are taken to resist the spread of flame and the generation of and spread of smoke throughout a building in case of an outbreak of fire. Clearly, the cable is designed to protect against loss of life and also minimize the costs of a fire due to the destruction of electrical and other equipment. Therefore, conductive media and cables for building installations are required to comply with the various flammability requirements of the National Electrical Code (NEC) in the U.S. as well as International Electrotechnical Commission (EIC) and/or the Canadian Electrical Code (CEC).
Cables intended for installation in the air handling spaces (i.e. plenums, ducts, etc.) of buildings are specifically required by NEC/CEC/IEC to pass the flame test specified by Underwriters Laboratories Inc. (UL), UL-910, or its Canadian Standards Association (CSA) equivalent, the FT6. The UL-910, FT-6, and the NFPA 262 represent the top of the fire rating hierarchy established by the NEC and CEC respectively. Also important are the UL 1666 Riser test and the IEC 60332-3C and D flammability criteria. Cables possessing these ratings, generically known as “plenum” or “plenum rated” or “riser” or “riser rated”, may be substituted for cables having a lower rating (i.e. CMR, CM, CMX, FT4, FTI or their equivalents), while lower rated cables may not be used where plenum or riser rated cables are required.
In 1975, the NFPA recognized the potential flame and smoke hazards created by burning cables in plenum areas, and adopted in the NEC a standard for flame retardant and smoke suppressant cables. This standard, commonly referred to as “the Plenum Cable Standard”, permits the use of cable without conduit, so long as the cable exhibits low smoke and flame retardant characteristics. The test method for measuring these characteristics is commonly referred to as the Steiner Tunnel Test. The Steiner Tunnel Test has been adapted for the burning of cables according to the following test protocols: NFPA 262, Underwriters Laboratories (U.L.) 910, or Canadian Standards Association (CSA) FT-6. The test conditions for each of the U.L. 910 Steiner Tunnel Test, CSA FT-6, and NFPA 262 are as follows: a 300,000 BTU/hour flame is applied for 20 minutes to ten 24-foot lengths of test cables mounted on a horizontal tray within a tunnel. The criteria for passing the Steiner Tunnel Test is as follows:                A. Flame spread—flame travel less than 5.0 feet.        B. Smoke generation:        1. Maximum optical density of smoke less than 0.5.        2. Average optical density of smoke less than 0.15.        
Because of concerns that flame and smoke could travel along the extent of a plenum area in the event the electrical conductors and cable were involved in a fire, the National Fire Protection Association (“NFPA”) has developed a standard to reduce the amount of flammable material incorporated into insulated electrical conductors and jacketed cables. Reducing the amount of flammable material would, according to the NFPA, diminish the potential of the insulating and jacket materials from spreading flames and evolving smoke to adjacent plenum areas and potentially to more distant and widespread areas throughout a building.
The products of the present invention have also been developed to support the evolving NFPA standard referenced as NFPA 255 entitled “Limited Combustible Cables” with less than 50 as a maximum smoke index and/or NFPA 259 entitled “Heat of Combustion” which includes the use of an oxygen bomb calorimeter that allows for materials with less than 3500 BTU/lb. for incorporation into the newer cable (and conductors and separators within these cables) designs. The proposed materials of the present invention are for inclusion with high performance support-separators and conduit tubes designed to meet the new and evolving standards proposed for National Electrical Code (NEC) adoption in 2005. Table 4 below provides the specific requirements for each of the
Cables conforming to NEC/CEC/IEC requirements are characterized as possessing superior resistance to ignitability, greater resistant to contribute to flame spread and generate lower levels of smoke during fires than cables having lower fire ratings. Often these properties can be anticipated by the use of measuring a Limiting Oxygen Index (LOI) for specific materials used to construct the cable. Conventional designs of data grade telecommunication cable for installations in plenum chambers have a low smoke generating jacket material, e.g. of a specially filled PVC formulation or a fluoropolymer material, surrounding a core of twisted conductor pairs, each conductor individually insulated with a fluorinated insulation layer. Cable produced as described above satisfies recognized plenum test requirements such as the “peak smoke” and “average smoke” requirements of the Underwriters Laboratories, Inc., UL910 Steiner tunnel test and/or Canadian Standards Association CSA-FT6 (Plenum Flame Test) while also achieving desired electrical performance in accordance with EI/TIA-568 A, B, and C for high frequency signal transmission.
The newer standards are forcing industrial “norms” to change and therefore require a new and unique set of materials that will be required to achieve the new standards. These materials are the subject of the present invention and include nano-composites of clay and other inorganics such as ZnO and TiO2 both also as nano-sized particles. In addition, the use of insulative or semi-conductive Buckminster fullerenes and doped fullerenes of the C60 family, nanotubes of the same and the like are part of the present invention and offer unique properties that allow for maintaining electrical integrity as well as providing the necessary reduction in flame retardance and smoke suppression.
While the above described conventional cable, due in part to its use of fluorinated polymers, meets all of the above design criteria, the use of fluorinated polymers is extremely expensive and may account for up to 60% of the cost of a cable designed for plenum usage. A solid core of these communications cables contributes a large volume of fuel to a potential cable fire. Forming the core of a fire resistant material, such as with FEP (fluorinated ethylene-propylene), is very costly due to the volume of material used in the core, but it should help reduce flame spread over the 20-minute test period. Reducing the mass of material by redesigning the core and separators within the core is another method of reducing fuel and thereby reducing smoke generation and flame spread. For the commercial market in Europe, low smoke fire retardant polyolefin materials have been developed that will pass the EN (European Norm) 502666-Z-X Class B relative to flame spread, total heat release, related heat release, and fire growth rate. Prior to this inventive development, standard cable constructions requiring the use of the aforementioned expensive fluorinated polymers, such as FEP, would be needed to pass this rigorous test. Using low smoke fire retardant polyolefins for specially designed separators used in cables that meet the more stringent electrical requirements for Categories 6 and 7 and also pass the new norm for flammability and smoke generation is a further subject of this invention. Tables 3A, 3B, and 4 indicate categories for flame and smoke characteristics and associated test methods as discussed above.
TABLE 3AInternational Classification and Flame TestMethodology for Communications CableAdditionalClassTest MethodsClassification CriteriaClassificationAcaEN ISO 1716PCS ≦ 2.0 MJ/kg (1) andPCS ≦ 2.0 MJ/kg (2)B1caFIPEC20 Scenario 2 (6)FS ≦ 1.75 m andSmoke production (3, 7)andTHR1200 ≦ 10 MJ andand FlamingPeak HRR ≦ 20 kW anddroplets/particles (4)FIGRA ≦ 120 Ws−1and Acidity (5)EN 50285-2-1H ≦ 425 mmB2caFIPEC20 Scenario 1 (6)FS ≦ 1.5 m andSmoke production (3, 8)andTHR1200 ≦ 15 MJ andand FlamingPeak HRR ≦ 30 kW anddroplets/particles (4)FIGRA ≦ 150 Ws−1and Acidity (5)EN 50285-2-1H ≦ 425 mmCcaFIPEC20 Scenario 1 (6)FS ≦ 2.0 m andSmoke production (3, 8)andTHR1200 ≦ 30 MJ andand FlamingPeak HRR ≦ 60 kW anddroplets/particles (4)FIGRA ≦ 300 Ws−1and Acidity (5)EN 50285-2-1H ≦ 425 mmDcaFTPEC20 Scenario 1 (6)THR1200 ≦ 70 MJ andSmoke production (3, 8)andPeak HRR ≦ 400 kW andand FlamingFIGRA ≦ 1300 Ws−1droplets/particles (4)EN 50285-2-1H ≦ 425 mmand Acidity (5)EcaEN 50285-2-1H ≦ 425 mmAcidity (5)FcaNo Performance Determined(1) For the product as a whole, excluding metallic materials.(2) For any external component (ie. Sheath) of the product.(3) S1 = TSP1200 ≦ 50 M2 and peak SPR ≦ 0.25 m2/sS2 = TSP1200 ≦ 400 M2 and peak SPR ≦ 1.5 m2/sS3 = Not S1 or S2(4) For FIPEC20 Scenarios 1 and 2:d0 = No flaming droplets/particles within 1200 sd1 = No flaming droplets/particles persisting longer than 10 s within 1200 sd3 = not d0 or d1(5) EN 50285-2-1: (?)A1 = conductivity < 2.5 μS/mm and pH > 4.3A2 = conductivity < 10 μS/mm and pH > 4.3A3 = not A1 or A2No declaration = No Performance Determined(6) Airflow into chamber shall be set to 8000 +/− 800 l/min.FIPEC20 Scen.1 = prEN50399-2-1 with mounting and fixing according to Annex 2FIPEC20 Scen.2 = prEN50399-2-2 with mounting and fixing according to Annex 2(7) The smoke class declared in class B1ca cables must originate from the FIPEC20 Scen.2 test(8) The smoke class declared in class B2ca cables must originate from the FIPEC20 Scen.1 test
TABLE 3BInternational Classification and TestMethodology for Communications CablePending CPD Euro-Classes for CablesPCS = gross calorific potentialFIGRA = firegrowth rateFS = flame spread (damaged length)TSP = total smokeproductionTHR = total heat releaseSPR = smoke productionrateHRR = heat release rateH = flame spreadPending CPD Euro-Classes for Communications & Energy Cables[A1]EN ISO 1716Mineral Filled CircuitIntegrity Cables[B1]FIPEC Sc.2/EN 50265-2-1LCC/HIFT - type LANComm. Cables[B2]FIPEC Sc.1/EN 50265-2-1Energy Cables[C]FIPEC Sc.1/EN 50265-2-1High FR/Riser-type Cables[D]FIPEC Sc.1/EN 50265-2-1IEC 332.3C type Cables[E]EN 50265-2-1IEC 332.1/VW1type Cables[F]No Requirement
TABLE 4Flammability Test Methods and Level of Severity for Wire and CableTest MethodIgnition Source OutputAirflowDurationUL2424/NFPA8 MJ/kg——259/255/UL723(35,000 BTU/lb.)Steiner Tunnel88 kW (300 k BTU/hr.)73 m/min.20 min.UL 910/NFPA 262(240 ft/min.) forcedRISER154 kW (527 K BTU/hr.)Draft30 min.UL2424/NFPA 259Single Burning Item30 kW (102 k BTU/hr.)36 m3/min.30 min.(20 min burner)Modified IEC 60332-330 kW (102 k BTU/hr.)8 m3/min.20 min.(Backboard behind ladder(heat impact))IEC 60332-320.5 kW (70 k BTU/hr.)5 m3/min.20 minVertical Tray20.5 kW (70 k BTU/hr.)Draft20 minIEC 60332-1/ULVW-1Bunsen Burner— 1 min(15 sec. Flame)
Table 5 indicates material requirements for wire and cable that can meet some of the test method criteria as provided in Table 4. “Low smoke and flame compound A” is a fluoropolymer based blend that includes inorganics known to provide proper material properties such that NFPA 255 and NFPA 259 test protocols may be met.
TABLE 5Material Requirements and Properties for Plenum, Riser, and Halogen Free CablesLow Smoke and FlameCompound ALSFR PVC(Halogen Free)(Halogen Free)NFPA 255/259HIFT/NFPA 262IEC 332.2CIEC 332.1PropertiesLCEuro Class B1Class C/DEuro Class ESpecific Gravity2.77 g/cc1.65 g/cc1.61 g/cc1.53 g/ccDurometer D Aged,69/6172/6359/4953/47Inst/15 sec.Tensile Strength,2,250 psi/2,500 psi/1,750 psi/1,750 psi/20″/min.15.5 Mpa17.2 Mpa12.1 Mpa12.1 MpaElongation, 20″/min. 250%180%180%170%Oxygen Index,100+% 53% 53% 35%(0.125″)Brittle point, deg C.−46−5−22−15Flexural Modulus,202000 psi/56000 psi/41000 psi/49000 psi/0.03″/min.1400 Mpa390 Mpa280 Mpa340 MPaUL Temp Rating, deg C.125+609075Dielectric Constant,2.923.253.873.57100 MHzDissipation Factor,0.0120.0140.0150.014100 MHz4 pr UTP Jkt Thickness9-11 mils/15-17 mils/30-40 mils/20-24 mils/.23-.28 mm.38-.43 mm.76-1.02 mm.50-.60 mm
Table 6 is provided as an indicator of low acid gas generation performance for various materials currently available for producing wire and cable and cross-web designs of the present invention. The present invention includes special polymer blends that are designed to significantly reduce these values to levels such as those shown for low smoke and flame Compound A as listed above in Table 5.
TABLE 6Acid Generation Values for Wire and Cable Insulation MaterialsMaterial% AcidPHFEP27.181.72ECTFE23.8901.64PVDF21.482.03LSFR PVC13.781.90Low Smoke and Flame1.543.01Compound A48% LOI HFFR0.353.4234% LOI HFFR.0243.94
Solid flame retardant/smoke suppressed polyolefins may also be used in connection with fluorinated polymers. Commercially available solid flame retardant/smoke suppressed polyolefin compounds all possess dielectric properties inferior to that of FEP and similar fluorinated polymers. In addition, they also exhibit inferior resistance to burning and generally produce more smoke than FEP under burning conditions. A combination of the two different polymer types can reduce costs while minimally sacrificing physio-chemical properties. An additional method that has been used to improve both electrical and flammability properties includes the irradiation of certain polymers that lend themselves to crosslinking. Certain polyolefins are currently in development that have proven capable of replacing fluoropolymers for passing these same stringent smoke and flammability tests for cable separators, also known as “cross-webs”. Additional advantages with the polyolefins are reduction in cost and toxicity effects as measured during and after combustion. The present invention utilizes blends of fluoropolymers with primarily polyolefins as well as the use of “additives” that include C60 fullerenes and compounds that incorporate the fullerenes and substituted fullerenes including nanotubes as well as inorganic clays and metal oxides as required for insulative or semi-conductive properties in addition to the flame and smoke suppression requirements. The use of fluoropolymer blends with other than polyolefins is also a part of the present invention and the incorporation of these other “additives” will be included as the new compounds are created. Reduction of acid gas generation is another key feature provided by the use of these blends as shown in Table 6 and another important advantage presented in the use of the cables and separators of the present invention. Price and performance characteristics for the separators and conduit tubes will determine the exact blend ratios necessary for these compounds.
A high performance communications data cable utilizing twisted pair technology must meet exacting specification with regard to data speed, electrical, as well as flammability and smoke characteristics. The electrical characteristics include specifically the ability to control impedance, near-end cross-talk (NEXT), ACR (attenuation cross-talk ratio) and shield transfer impedance. A method used for twisted pair data cables that has been tried to meet the electrical characteristics, such as controlled NEXT, is by utilizing individually shielded twisted pairs (ISTP). These shields insulate each pair from NEXT. Data cables have also used very complex lay techniques to cancel E and B (electric and magnetic fields) to control NEXT. In addition, previously manufactured data cables have been designed to meet ACR requirements by utilizing very low dielectric constant insulation materials. Use of the above techniques to control electrical characteristics have inherent problems that have lead to various cable methods and designs to overcome these problems. The blends of the present invention are designed such that these key parameters can be met.
Recently, as indicated in Tables 1, 2A and 2B, the development of “high-end” electrical properties for Category 6 and 7 cables has increased the need to determine and include power sum NEXT (near end crosstalk) and power sum ELFEXT (equal level far end crosstalk) considerations along with attenuation, impedance, and ACR values. These developments have necessitated more highly evolved separators that can provide offsetting of the electrical conductor pairs so that the lesser performing electrical pairs can be further separated from other pairs within the overall cable construction.
Recent and proposed cable standards are increasing cable maximum frequencies from 100-200 MHz to 250-700 Mhz. Recently, 10 Gbit over copper high-speed standards have been proposed. The maximum upper frequency of a cable is that frequency at which the ACR (attenuation/cross-talk ratio) is essentially equal to 1. Since attenuation increases with frequency and cross-talk decreases with frequency, the cable designer must be innovative in designing a cable with sufficiently high cross-talk. This is especially true since many conventional design concepts, fillers, and spacers may not provide sufficient cross-talk at the higher frequencies. Proposed limits for alien crosstalk have also been added to the present standards as shown in Table 2G. Such limits in many cases can only be met using the separators of the present invention.
Current separator designs must also meet the UL 910 flame and smoke criteria using both fluorinated and non-fluorinated jackets as well as fluorinated and non-fluorinated insulation materials for the conductors of these cable constructions. In Europe, the trend continues to be use of halogen free insulation for all components, which also must meet stringent flammability regulations. The use of the blends of the present invention for both separators and tube conduits will allow for meeting these requirements.
In plenum applications for voice and data transmission, electrical conductors and cables should exhibit low smoke evolution, low flame spread, and favorable electrical properties. Materials are generally selected for plenum applications such that they exhibit a balance of favorable and unfavorable properties. In this regard, each commonly employed material has a unique combination of desirable characteristics and practical limitations. Without regard to flame retardancy and smoke suppressant characteristics, olefin polymers, such as polyethylene and polypropylene, are melt extrudable thermoplastic materials having favorable electrical properties as manifested by their very low dielectric constant and low dissipation factor.
Dielectric constant is the property of an insulation material which determines the amount of electrostatic energy stored per unit potential gradient. Dielectric constant is normally expressed as a ratio. The dielectric constant of air is 1.0, while the dielectric constant for polyethylene is 2.2. Thus, the capacitance of polyethylene is 2.2 times that of air. Dielectric constant is also referred to as the Specific Inductive Capacity or Permittivity.
Dissipation factor refers to the energy lost when voltage is applied across an insulation material, and is the cotangent of the phase angle between voltage and current in a reactive component. Dissipation factor is quite sensitive to contamination of an insulation material. Dissipation factor is also referred to as the Power Factor (of dielectrics).
Fluorinated ethylene/propylene polymers exhibit electrical performance comparable to non-halogenated to olefin polymers, such as polyethylene, but are over 15 times more expensive per pound. Polyethylene also has favorable mechanical properties as a cable jacket as manifested by its tensile strength and elongation to break. However, polyethylene exhibits unfavorable flame and smoke characteristics.
Limiting Oxygen Index (ASTM D-2863) (“LOI”) is a test method for determining the percent concentration of oxygen that will support flaming combustion of a test material. The greater the LOI, the less susceptible a material is to burning. In the atmosphere, there is approximately 21% oxygen, and therefore a material exhibiting an LOI of 22% or more cannot burn under ambient conditions. As pure polymers without flame retardant additives, members of the olefin family, namely, polyethylene and polypropylene, have an LOI of approximately 19. Because their LOI is less than 21, these olefins exhibit disadvantageous properties relative to flame retardancy in that they do not self-extinguish flame, but propagate flame with a high rate of heat release. Moreover, the burning melt drips on the surrounding areas, thereby further propagating the flame.
Table 7 below summarizes the electrical performance and flame retardancy characteristics of several polymeric materials. Besides fluorinated ethylene/propylene, other melt extrudable thermoplastic generally do not provide a favorable balance of properties (i.e., high LOI, low dielectric constant, and low dissipation factor). Moreover, when flame retardant and smoke suppressant additives are included within thermoplastic materials, the overall electrical properties generally deteriorate.
TABLE 7Fire Retardancy CharacteristicsElectrical PropertiesDielectricDissipationNBS Smoke ValuesConstantFactorOptical Density, DMC1 MHz,1 MHz,Non-Material23Deg. C.23Deg. C.LOI %FlamingflamingPE2.2.00006-.0002 19387719FRPE2.6-3.0.003-.03728-32——FEP2.1.00055>80——PVC2.7-3.5.024-.07032740280RSFRPVC3.2-3.6.018-.08039200190LSFRPVC3.5-3.8.038-.08049<200 <170 
In the above table, PE designates polyethylene, FRPE designates polyethylene with flame retardant additives, FEP designates fluorinated ethylene/propylene polymer, PVC designates polyvinylchloride, RSFRPVC designates reduced smoke flame retardant polyvinylchloride, LSFRPVC designates low smoke flame retardant polyvinylchloride, LOI designates Limiting Oxygen Index, NBS designates the National Bureau of Standards, and DMC designates Maximum Optical Density Corrected.
In general, the electrical performance of an insulating material is enhanced by foaming or expanding the corresponding solid material. Foaming also decreases the amount of flammable material employed for a given volume of material. Accordingly, a foamed material is preferably employed to achieve a favorable balance of electrical properties and flame retardancy.
In addition to the requirement of low smoke evolution and flame spread for plenum applications, there is a growing need for enhanced electrical properties for the transmission of voice and data over twisted pair cables. In this regard, standards for electrical performance of twisted pair cables are set forth in Electronic Industry Association/Telecommunications Industry Association (EIA/TIA) document TSB 36 and 40. The standards include criteria for attenuation, impedance, crosstalk, and conductor resistance.
In the U.S. and Canada, the standards for flame retardancy for voice communication and data communication cables are stringent. The plenum cable test (U.L. 910/CSA FT-6) and riser cable test U.L. 1666 are significantly more stringent than the predominantly used International fire test IEC 332-3, which is similar to the IEEE 383/U.L. 1581 test.
Table 8 already summarizes the standards required for various U.L. (Underwriters Laboratories and CSA (Canadian Standards Authority) cable designations.
TABLE 8U.L./CSADesignationCable Fire TestFlame EnergyCMP/MPPPlenum U.L. 910300,000 BTUHCSA FT-6 Horizontal RiserCMR/MPRU.L. 1666 Vertical527,000 BTUHCMG/MPGFT-4 Vertical 70,000 BTUHBurner angle 20 degreesCM/MPIEEE 1581 Vertical 70,000 BTUHBurner angle 0 degrees
As indicated above, current separator designs must also meet the UL 910 flame and smoke criteria using both fluorinated and non-fluorinated jackets as well as fluorinated and non-fluorinated insulation materials for the conductors of these cable constructions. The UL 910 criteria has been included in the recently adopted NFPA 262 criteria and extended with more severity in the NFPA 255 and 259 test criteria. To ensure that the test criteria is met, the use of the separators of the current invention is not only useful but often necessary. For meeting the NFPA 72 test criteria for circuit integrity cable, the support-separators and the materials from which they will be produced is an integral part of the present invention. The reduction in material loading (lbs/MFT) as shown in Table 9 can be an essential aspect in meeting this demand. Substantial reduction of this load by the use of separators can be achieved. The use of the polymer blends of the present invention for both separators and conduit tubes will allow for meeting the requirements for not only current circuit integrity cables but also for cables that must meet the newer more stringent requirements in the future.
TABLE 9Insulation Material Criteria For Circuit Integrity CableInsula-JacketCableApproxi-NominalNumbertionThick-Di-mateCable Layof Con-AWGThicknessnessameterWeight(in./ductorssize(mils)(mils)(in)(lbs/MFT)twist)2163540.34593.72143540.36754.02123550.421064.4
Principal electrical criteria can be satisfied based upon the dielectric constant and dissipation factor of an insulation or jacketing material. Secondarily, the electrical criteria can be satisfied by certain aspects of the cable design such as, for example, the insulated twisted pair lay lengths. Lay length, as it pertains to wire and cable, is the axial distance required for one cabled conductor or conductor strand to complete one revolution about the axis of the cable. Tighter and/or shorter lay lengths generally improve electrical properties.
Individual shielding is costly and complex to process. Individual shielding is highly susceptible to geometric instability during processing and use. In addition, the ground plane of individual shields, 3600 in ISTP's—individually shielded twisted pairs is also an expensive process. Lay techniques and the associated multi-shaped anvils of the present invention to achieve such lay geometries are also complex, costly and susceptible to instability during processing and use. Another problem with many data cables is their susceptibility to deformation during manufacture and use. Deformation of the cable geometry, such as the shield, also potentially severely reduces the electrical and optical consistency.
Optical fiber cables exhibit a separate set of needs that include weight reduction (of the overall cable), optical functionality without change in optical properties and mechanical integrity to prevent damage to glass fibers. For multi-media cable, i.e. cable that contains both metal conductors and optical fibers, the set of criteria is often incompatible. The use of the present invention, however, renders these often divergent set of criteria compatible. Specifically, optical fibers must have sufficient volume in which the buffering and jacketing plenum materials (FEP and the like) covering the inner glass fibers can expand and contract over a broad temperature range without restriction, for example −40 C. to 80 C. experienced during shipping. It has been shown by Grune, et. al., among others, that cyclical compression and expansion directly contacting the buffered glass fiber causes excess attenuation light loss (as measured in dB) in the glass fiber. The design of the present invention allows for designation and placement of optical fibers in clearance channels provided by the support-separator having multiple shaped profiles. It would also be possible to place both glass fiber and metal conductors in the same designated clearance channel if such a design is required. In either case the forced spacing and separation from the cable jacket (or absence of a cable jacket) would eliminate the undesirable set of cyclical forces that cause excess attenuation light loss. In addition, fragile optical fibers are susceptible to mechanical damage without crush resistant members (in addition to conventional jacketing). The present invention addresses this problem by including the use of both organic and inorganic polymers as well as inorganic compounds blended with fluoropolymers to achieve the necessary properties in a non-conventional separator design.
The need to improve the cable and cable separator design, reduce costs, and improve both flammability and electrical properties continues to exist.